In order to reduce the weight of airplane turbojets, and thus to reduce the fuel consumption of such turbojets, it is already known to fabricate certain blades of jets out of composite material, which is much lighter than the metal that has conventionally been used heretofore.
For this purpose, it is nowadays also known to use three-dimensional (3D) weaving techniques in order to obtain fiber preforms that lead to composite blades of very good quality. In particular, Document WO 2014/076408 describes a method of weaving a airfoil preform that makes it possible to obtain blades in single-piece manner that include both pressure side and suction side platforms, which platforms are of constant thickness.
Nevertheless, during tests and simulations undertaken on such blades, the inventors have found that various zones of the platforms deform to a greater or lesser extent under the effect of the centrifugal forces that act while the turbine engine is in operation. In particular, the inventors have observed that the deformation of a zone of the platform increases with increasing offset from the airfoil.
Under such circumstances, when in operation, those platforms present irregularities of shape that might disturb the stream of air and thus the efficiency of the turbine engine. In addition, the inventors have observed that suction side platforms, which are generally the longer platforms, are subjected to greater bending than pressure side platforms, such that discontinuities appear at the interface between the suction side and pressure side platforms of two consecutive blades, there also being a risk of the pressure side platforms being overlapped by the adjacent suction side platforms.
There therefore exists a real need for a fiber preform, a blade, a rotor wheel, and a turbine engine that are free, at least in part, of the above-mentioned drawbacks inherent to known systems.